[X] My Assistant

[Bjorn Jonsson]

I'm curious to know how people have been dealing with badly smeared images to reduce or eliminate the smear. I'm making 20000x10000 pixel global maps of Ganymede and Callisto. Lots of the highest resolution Voyager 1 images are badly smeared but I really want to use them in the maps if possible - and use them without smear (otherwise the maps get too ugly). I've been experimenting with the Smart Sharpen filter in Photoshop. I'm rather happy with the results I've had but before I start reprojecting these images and adding them to the maps I'm curious to know if anyone knows of something even better.

Here are two examples from Voyager 1 where I attempted to desmear smeared images using the PS Smart Sharpen filter. The original is shown together with a desmeared image. One is from a moderately smeared partial image of Callisto and another one is a badly smeared image of Ganymede. As indicated above I'm rather happy with the results but if something better is possible I'd like to know.

Callisto:



Ganymede:

[Bjorn Jonsson]

The Parallel Iterative Deconvolution plugin mentioned above is awesome. I have been able to get similar results to machi's results above for images that had a similar 'type' of smear (it was slightly less in my case). Comparing the results to other images that are not smeared and were obtained at a similar time with a different filter reveals that the smeared images were almost completely restored.

But interestingly, I've had some problems with images where the smear is much less. This image of Ganymede is an example:



I experimented with lots of PSF images but got the best results using this one:



But the resutling image isn't particularly good. There's less smear and some details are restored but there's also a lot of noise:



In a different thread, jccwrt has been experimenting with smeared images of Io using this same plugin. He ran into similar problems and wrote:

The most severe smearing was in the first frame of each sequence, so I'm guessing that's a result of imaging before the scan platform had entirely stabilized after slewing.

This could be my problem too. Another related possibility is that in some of the less smeared images (the ones that are difficult to desmear), the scan platform started moving just before the end of the exposure or stopped moving just after the start of the exposure and introduced 'vibrations' or other irregular motion while in the more smeared images the motion was even and regular throughout the exposure, with the regular motion making the images relatively easy to desmear.

Needless to say, if anyone is interested in trying to get better results and succeeds I'm interested in knowing about it.